1. Field of the Invention
The present invention relates to exposure methods, exposure apparatuses, and device manufacturing methods, and more particularly, to an exposure method and an exposure apparatus used in a lithography process when semiconductor devices, liquid crystal display devices and the like are produced, and a device manufacturing method using the exposure method.
2. Description of the Background Art
Conventionally, in a lithography process for manufacturing microdevices (such as electron devices) such as semiconductor devices, liquid crystal display devices and the like, exposure apparatuses such as a reduction projection exposure apparatus by a step-and-repeat method (a so-called stepper) and a projection exposure apparatus by a step-and-scan method (a so-called scanning stepper (which is also called a scanner) are mainly used.
In this kind of exposure apparatus, in order to transfer a pattern of a reticle (or a mask) on a plurality of shot areas on a wafer, a wafer stage holding the wafer is driven, for example, by linear motors and the like. In this case, position measurement of the wafer stage is generally performed, using a laser interferometer which is stable and has high resolution.
However, requirements for a stage position control with higher precision are increasing due to finer patterns that accompany higher integration of semiconductor devices, and now, measurement errors resulting from air fluctuation generated by temperature variation of the atmosphere on the beam path of the laser interferometer or by temperature gradient has come to occupy a large percentage in the overlay budget.
As a position measurement device of the stages in place of the laser interferometer, an encoder (for example, refer to U.S. Patent Application Publication No. 2008/0088843) is promising. However, while the encoder is superior in the viewpoint of measurement reproducibility because of using a scale, it is inferior for the mechanical instability (drift of the grating pitch, fixed location drift, thermal expansion and the like) of the scale in the viewpoint of linearity. Further, as a surface position measurement device of the stage, while a surface position measurement sensor (refer to, for example, U.S. Patent Application Publication No. 2008/0086843) which measures the surface position of the scale is promising, it is similarly inferior in the viewpoint of linearity.
In view of the drawbacks of the laser interferometer and the encoder (and the surface position measurement sensor) described above, various proposals are being made (refer to, for example, Kokai (Japanese patent Unexamined Application Publication) No. 2009-033062) of methods used to measure the position of a stage using both a laser interferometer and an encoder (a position detection sensor which uses a diffraction grating). However, the methods and the like disclosed in Kokai (Japanese Patent Unexamined Application Publication) No. 2009-033062 are still not sufficient enough when carrying out a highly accurate and stable position control of the stage which is required in the current exposure apparatus.